Molding unit



Dec. 5, 1961 R. E. HAWKINS EFAL 3,

MOLDING UNIT Filed Dec. 19, 1958 2 Sheets-Sheet 1 RONALD E2. HAWKINS GENE R. PENDL INVENTORS J'LTTORNE'Y Dec. 5, 1961 R. E. HAWKINS El'AL 3,

MOLDING UNIT Filed Dec. 19, 1958 v 2 Sheets-Sheet 2 GENE R. PENDL INVENTORS ATTORNEY RONALD E. HAWKINS Unite States Patent 3,011,232 MOLDING UNIT Ronald E. Hawkins and Gene R. Pendl, South Bend,

Ind., asslgnors to The Bendix Corporation, a corporation of Delaware Filed Dec. 19, 1958, Ser. No. 781,557 6 Claims. (Cl. 22-165) This invention relates in general to molds adapted to form castings of magnesium.

Our invention is directed to a core structure which, during the casting operation, prevents the formation of gas pockets and/or oxide skins on the surface of the cavity formed by the core; and prevents to a degree the formation of pockets of gas or any gas traces within the body of the casting.

Our invention provides an effective and simple method for producing magnesium castings free of the aforementioned undesired gas filled pockets within the casting and gas produced blisters on the surface of said casting; and said process involves the use of a minimum of difierent elements and a minimum of simple steps in the casting operation. Our invention also includes the method of producing a permeable core which will insure a free flow of gas from a casting as it is being prepared.

An important feature of our invention lies in the provision of means, constituting a part of the mold, for conducting gases into the principal core element of the mold, said gases being developed within the casting material as it is being poured into the mold; and a very important feature of our invention lies in the provision, in the core structure of our invention, of a gas conductible core element which does not burn the magnesium around saiddelement as the magnesium is being poured into the mo Yet another object of our invention is to provide a.

construction of parts will become apparent from the fol- FIGURE 1 discloses a piece of aluminum tubing to be used in our invention;

FIGURE 2 is a view of the tube of FIGURE 1 bent at its ends 'to be fastened to a core element of our invention and punched to locate certain holes to be made in said tube;

FIGURE 3 is a view of the tube of FIGURE 2 drilled to provide gas transmitting holes;

FIGURE 4 discloses the tube of FIGURE 3 secured to a core reinforcing wire;

FIGURE 5 discloses the tube and wire unit of FIGURE 3 secured to the body portion of the core of our invention;

FIGURE 6 discloses one half of the casting, the product of the mold of our invention; and

FIGURE 7 is a view disclosing the complete magnesium casting.

There is disclosed, in the several figures of the drawing and in the process described hereinafter, a preferred embodiment of our invention. One feature of this invention lies in the core unit disclosed in FIGURE 5. To produce this unit a straight piece of aluminum or aluminum alloy tubing, say, of one fourth inch outside diameter, is cut to the approximate required length. This tube, disclosed in FIGURE 1, is then filled with Cerro Bend or other material having a very low melting point and bent at its ends 12 and 14 to the shape disclosed in FIGURE 2; that is the ends are turned at a right angle to the body'of the tube. Cerro Bend is the trademark of a commercially 3,011,232 PatentedDec. 5, 1961 ice available alloy composed of 50% bismuth, 26.7% lead, 13.3% tin and 10% cadmium which facilitates this bending operation.

After bending the tube is ready to be marked and punched for drilling holes in the same. Holes 16 are, in the preferred embodiment of our invention, placed two inches apart in four rows along the tube. On opposite sides the holes are opposite in pairs. The other two rows are placed so that a ring around the tube connecting each pair of holes would be midway between a ring connecting the holes in the other two rows. The tube is now ready to be heated in order to remove the Cerro Bend. After draining this material the tube is dipped into alchemize to make sure that it is clean both inside and out.

The aluminum tube, FIGURE 3, is now sand blasted and the aforementioned punched holes 16 are then drilled with the point of a size .020 inch pilot drill which produces a .020 inch hole.

As is disclosed in FIGURE 4 the ends of the tube or core element are now brazed to a length of core Wire 18 of suitable material such as steel. The tube is now preferably hard coated with aluminum oxide by any one of the well known electrolytic processes. This makes a protective nonmetallic hard coat preferably less than five thousandths of an inch thick which prevents the molten magnesium of the casting from eroding the tube; and it is an important feature of our invention that the presence of this hard coat of aluminum oxide prevents an undesirable oxidizing or so-calledburning of the magnesium being poured.

The relatively small holes 16 allow gases from the casting metal to enter the tube and escape into the interstices of a generally tubular shaped core member 20, FIGURE 5. This member, shaped to effect the desired cavity, that is bore, of the casting to be made, is fabricated in the usual manner except that the bent ends 12 and 14 of the aluminum tube are embedded that is printed in the core member 20 during said fabrication. The core members 10 and 20 together provide a core unit which will insure a free flow of gas from the casting as it is being formed. The core element 20 is preferably made of sand or its equivalent together with a suitable binder such as corn flour. The wire 18 reinforces the core element 20 and facilitates the handling of the core unit Without breaking the same.

As to the casting operation the core unit 10, 20 is placed in the usual mold box 21 whereupon the molten magnesium at about 1,400 F. temperature is poured into sand mold. to form a casting 22. The cavity of the casting is indicated in FIGURE 6 by the reference numeral 24. The mold is then shaken to crumble the sand core 20 and the fragments of said core are then dumped out of the mold through an opening, not shown. The casting 22 is then from the casting after the destruction of the sand core' 20. The casting may then be X-rayed to determine the presence, if any, of remaining portions of the tube 10.

There is thus provided, by our invention, a hollow magnesium casting free of gas blisters, blows on the surfaces of the casting and gas pockets within the body of said casting. The whole casting unit is shown in FIG- URE 7 and one half of a split unit is shown in FIG- URE 6. Important features of our invention lie in (l) the several steps for making the core unit 10, 20 and (2) the virtues of said core unit itself-as an article of manufacture. The perforated U-shaped'tube 10 serves to draw the gas out of. the mold cavity during the molding operaand the aluminum oxide hard coat for the tube 10 prevents an erosion of the tube by the molten metal forming the casting and also prevents a burning of the magnesium during the pouring operation.

While the preferred embodiment of the invention has been described in considerable detail, We do not wish to be limited to the particular construction shown which may be varied within the scope of the invention, and it is the intention to cover hereby all adaptations, modifications and arrangements thereof which come within the practice of those skilled in the art to which the invention relates.

We claim:

1. A mold adapted to form hollow magnesium castings free of gas and imperfections, said mold including a core unit comprising a core member predominantly of sand and a permeable aluminum tube member having a hard coating of aluminum oxide and having its ends anchored into the body of the core member and operable to drain gas from the casting metal into the latter member during the casting operation.

2. A mold adapted to form hollow magnesium castings free of gas and imperfections, said mold includinga core unit comprising a core member predominantly of sand, an aluminum tube member, soluble in hydrofluoric acid, having its ends anchored into the body of said core member and operable, by virtue of its permeability to drain gas from the magnesium casting metal into the latter member during the casting operation, together, with a non-metallic hard coat of aluminum oxide coating on the tube, said coating serving to prevent erosion of the tube during the casting operation and serving to prevent a burning of the casting metal as it is being poured into the mold.

3. A mold unit adapted to form hollow magnesium castings free of gas and imperfections, said mold including a core unit comprising a core member predominantly of sand, a tube member of aluminum, soluble in hydrofluoric acid, having its ends anchored into the body ofthe sand core member and operable to drain gas from the magnesium casting metal into the latter member during the casting operation, together with a hard coating of aluminum oxide on the tube, said coating serving to prevent erosion of the tube during the casting operation and serving to prevent an oxidation of the casting metal as it is poured into the mold.

4. A method of producing a hollow metal casting of magnesium free of gas and imperfections in the casting caused by gas, said method including the successive steps of filling an aluminum tube. with a low melting point alloy, bending said tube to a desired configuration, removing said alloy from the tube, drilling a plurality of relatively small spaced apart holes in the tube, hard coating said aluminum tube with aluminum oxide, embedding the tube ends in a core member of sand or its equivalent, placing the core member with its attached tube in a mold box, pouring molten magnesium into the mold box, removing the core rnemberand removing the aluminum tube by destroying the same with hydrofluoric acid or its equivalent.

5. A method of making a core unit used in a mold adapted to make a magnesium casting to be free of gas and imperfections caused by gas, said method in cluding the successive steps of filling an aluminum tube with a low melting point alloy, bending said tube to a desired configuration, removing the low melting point alloy from the tube, drilling a plurality of relatively small-diametered spaced apart holes in the tube, hard coating the aluminum tube with aluminum oxide and embedding the tube ends in a sand core member during the process of forming said member.

6. A method of producing a hollow metal casting of magnesium free of gas and imperfections in the casting caused by gas, said method including the successive steps of forming an aluminum tube having open end portions to a desired configuration, drilling a plurality of relatively small spaced apart holes in the tube, hard coating said aluminum tube with aluminum oxide, em= bedding the tube ends in a sand core member, placing the core member with its attached tube in a mold box, pouring molten magnesium into the mold box, removing the core member and removing the aluminum tube by destroying the same with hydrofluoric acid or its equivalent.

References Cited in the file of this patent UNITED STATES PATENTS 2,045,556 Almen June 23, 1936 2,268,676 Shanley Jan. 6, 1942 2,362,875 Zahn Nov. 14, 1944 FOREIGN PATENTS 587,637 Great Britain May 1, 1947 

